For the first time in human history, concentrations of carbon dioxide in the atmosphere are expected to pass 400 parts per million across much of the Northern Hemisphere in May, according to scientists who study data from the Mauna Loa Observatory, the world's longest-running CO2 monitoring station.

While crossing the 400 ppm mark isn't a "tipping point" that signals climate catastrophe, scientists told InsideClimate News, it is an important symbolic milestone that underscores government inaction on global warming.

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For the first time in human history, concentrations of carbon dioxide in the atmosphere are expected to pass 400 parts per million across much of the Northern Hemisphere in May.

What's frightening is that most of the news outlets that reported this were environmental websites. It did also lead me to an interesting article by Dr Alex Awiti in The Star (Kenya) in which he imagines what it might be like to report the latest climate news 100 years from now, on July 9 2103. At the risk of spoiling it for you - it's not good news.

I'd be interested to hear people's views on an article in the Telegraph by James Delingpole where he seems to be dismissing this landmark as "hysteria".